The invention relates to a dashpot for the fuel tanks having an upper wall which closes off, at the top, a gas separation space which has lateral wall parts and a lower fuel guide surface and is connected to an opening above the maximum fuel level provided therein, to which gas separation space returning fuel can be fed via a fuel return line, and having a pot opening near the base, via which opening fuel can be drawn off into the pot interior from the supply of fuel present in the fuel tank by means of an ejector jet generated by returning fuel by means of an injector nozzle.
A dashpot of this kind is disclosed in DE-PS No. 2,401,728. In this design, the pot opening, which is near the base and arranged downstream of the injector nozzle, is located at an end of the gas separation space, said end being accessible from the outside of the pot, which gas separation space opens with its other end into the pot interior. The opening is located in the center of the upper wall of the pot which closes off both the pot interior and the gas separation space.
The fuel which is not consumed in supplying internal combustion engines with fuel, in particular those having fuel injection, is usually heated, in particular on its return journey along hot zones, giving rise to gas bubbles in the fuel line. When the ejector jet formed by this fuel enters the gas separation space, the gas bubbles expand, float upwards and are carried along by the current into the pot interior. They escape from this via the central opening in the upper wall of the pot and pass into the fuel tank.
Now, in so far as the level of the fuel in the fuel tank is substantially above the height of the dashpot, the gas bubbles make their way upwards in the fuel, this being associated with more or less pronounced bubbling noises which can be heard in the passenger compartment and are therefore troublesome.
It is thus an object of the present invention to improve a dashpot of a design referred to above such that gas bubbles can no longer cause troublesome noises within the fuel tank. This object is achieved in preferred embodiments of the invention by providing that the gas separation space is separated from the pot interior and by providing a degassing line leading away from the gas separation space and discharging above the maximum fuel level into the fuel tank.
In a dashpot of this kind, returning fuel can become calmer and lose its gas while it flows along the fuel guide surface, the gas being caught in the gas separation space and discharged silently via the degassing line into the upper, fuel-free part of the fuel tank.
Even given a relatively high flow rate of the returning fuel within the gas separation space, certain preferred embodiments include a gas bubble retaining device to assure satisfactory degassing.
The calming of the fuel for the purpose of degassing in the gas separation space is favored in certain preferred embodiments by configuring the gas separation space cross-section to increase in the direction of the flow of the fuel. Preferred embodiments offer the advantage that an adequate suction effect for drawing in fuel from the fuel tank can still be achieved by means of the returning fuel even where the degassing section is relatively long by sloping the fuel guide surface downwardly in the direction of the injector nozzle and by disposing the injector nozzle to connect to the gas separation space behind the lower end of the inclined surface.
In certain preferred embodiments it is possible to equip the dashpot with a relatively long degassing section while employing a particularly compact design of the dashpot by forming the dashpot of essentially circular cylindrical shape and extending the gas separation space along the outside of the pot wall.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.